1. Field of the Invention
The present invention relates to a process for producing a highly chlorinated copper phthalocyanine by a chlorination of a copper phthalocyanine, particularly, it relates to an industrial advantageous process for producing a highly chlorinated copper phthalocyanine by a chlorination of a copper phthalocyanine in a solvent of a sulfur oxyacid chloride such as pyrosulfuryl chloride which can be formed by a reaction of chlorosulfonic acid with chlorine and sulfur or sulfur chloride.
2. Description of Prior Arts
A copper phthalocyanine is a blue pigment. A greenish blue pigment is obtained by chlorinating a copper phthalocyanine to substitute 12 or more of hydrogen atoms of benzene rings with chlorine atoms preferably to substitute with 13 or more of chlorine atoms among 16 of sites. A brilliant yellowish green pigment is obtained by substituting with 14 or more of chlorine atoms.
The highly chlorinated copper phthalocyanine pigment is called as copper phthalocyanine green or phthalocyanine green and it is a pigment having excellent light fastness and solvent resistance.
In the well-known industrial process for producing a highly chlorinated copper phthalocyanine by a chlorination of a copper phthalocyanine, a copper phthalocyanine is dissolved in a molten mixture of anhydrous aluminum chloride and sodium chloride and it is contacted with chlorine gas at 150.degree. to 200.degree. C. to chlorinate the copper phthalocyanine and the reaction mixture is poured into a large amount of ice water and the chlorinated copper phthalocyanine is separated.
This process is widely carried out as an industrial process since a brilliant yellowish green pigment can be easily obtained.
However, the following disadvantages are found.
(1) A cost for a recovery of aluminum chloride and sodium chloride is too high to carry out as an industrial purpose and a cost for treating aluminum chloride in a waste water is remarkably high because 5 to 8 times by weight of anhydrous aluminum chloride to a copper phthalocyanine is used and the reaction mixture is poured in water.
(2) A chlorination is carried out at high temperature of 150.degree. to 200.degree. C. whereby various by-products are formed to decrease a yield.
On the other hand, it has been known to produce a highly chlorinated copper phthalocyanine by dissolving a copper phthalocyanine in chlorosulfonic acid and charging chlorine into the solution in the presence of a catalyst in U.S. Pat. No. 2,662,082.
This process has advantages.
(1) A reaction temperature is upto 115.degree. C. and an operation is easier and a corrosion of an apparatus is lower in comparison with those of the aluminum chloride-sodium chloride process.
(2) A cost of chlorosulfonic acid is lower than that of anhydrous aluminum chloride.
However, this process has not been carried out as an industrial process because of the following reason.
(1) A yield is remarkably lower than that of the aluminum chloride-sodium chloride process.
(2) A hue of the resulting pigment is not good and bluish and a brilliant yellowish green has not been given.
It has been also known to produce a highly chlorinated copper phthalocyanine by chlorinating a copper phthalocyanine in a solvent of pyrosulfuryl chloride with thionyl chloride in Japanese Patent Publication No. 15790/1962.
This process is not an industrial process because a large amount of thionyl chloride is used.
Heretofore, it has been considered that when chlorine gas is charged in a solution of a copper phthalocianine in a strong acidic solvent such as sulfuric acid and fuming sulfuric acid, an oxidation of a copper phthalocyanine is caused to reduce a yield (Phthalocyanine compound, Moser, Thomas Page 178. Japanese Patent Publication No. 15790/1962).
In accordance with the process of U.S. Pat. No. 2,662,082, the chlorination of a copper phthalocyanine is carried out in chlorosulfonic acid under the atmospheric pressure with a small amount of a chlorination catalyst of sulfur chloride, only bluish green chlorinated copper phthalocyanine is obtained in a yield of about 50%.
The inventors have studied to improve the process using a solvent of chlorosulfonic acid and have found that a brilliant yellowish green highly chlorinated copper phthalocyanine can be obtained in high yield by charging chlorine under an elevated pressure in the presence of pyrosulfuryl chloride and excess of a catalyst of sulfur or sulfur chloride. This invention has been attained by this finding.